1. Field of the Invention
The present invention relates to a twin clutch transmission, and a vehicle and motorcycle equipped therewith.
2. Description of the Related Art
Heretofore, a transmission has been known that is equipped with a plurality of clutches in order to make possible speedy transmission operations of an automobile (see Unexamined Japanese Patent Publication No. SHO58-124851, for example).
A vehicular multi-speed transmission of Unexamined Japanese Patent Publication No. SHO58-124851 is equipped with an input shaft by which a driving force of an engine is input, a first auxiliary shaft that is rotatable with respect to the input shaft, a second auxiliary shaft provided on the same axis line as the input shaft, a counter shaft provided parallel to the input shaft, an output shaft connected to the counter shaft, a first clutch provided between the input shaft and the first auxiliary shaft, and a second clutch provided between the input shaft and the second auxiliary shaft.
The input shaft that inputs the engine driving force is passed through the inside of the first auxiliary shaft and is connected to the second auxiliary shaft via the second clutch.
With this vehicular multi-speed transmission, the first auxiliary shaft rotates by having the torque of the input shaft transferred by means of connection of the first clutch, and the second auxiliary shaft rotates by having the torque of the input shaft transferred by means of connection of the second clutch.
The torque of the first auxiliary shaft is transferred to the counter shaft at a predetermined gear ratio by means of a plurality of gears. By this means, the counter shaft and output shaft rotate at a predetermined rotation speed. The torque of the second auxiliary shaft is transferred to the counter shaft at a predetermined gear ratio by means of a plurality of gears. By this means, the counter shaft and output shaft rotate at a predetermined rotation speed.
Thus, in the above-described vehicular multi-speed transmission, the torque of the input shaft can be transferred to the counter shaft at different gear ratios by connecting the first clutch and second clutch selectively. By this means, the rotation speed of the output shaft can be changed.
There is a demand for mounting a multi-speed transmission, provided with a plurality of clutches and generally mounted on a vehicle, on a motorcycle having limited mounting space, and a reduction in the size of the multi-speed transmission itself is desired.
However, since the above-described vehicular multi-speed transmission configuration includes a double-tube structure in which the input shaft is passed through the inside of the first auxiliary shaft, the diameter of the first auxiliary shaft is further increased by the diameter of the input shaft passed through rotatably, and the diameter of a gear provided on the first auxiliary shaft is also increased.
Here, a gear ratio between the first auxiliary shaft and the counter shaft is decided by a gear provided on the first auxiliary shaft and the diameter of a gear (a gear provided on the counter shaft) that meshes with that gear.
Therefore, if the diameter of a gear on the first auxiliary shaft is increased, it is also necessary to increase the diameter of a gear provided on the counter shaft in order to maintain a predetermined gear ratio, and the distance between the first auxiliary shaft and the counter shaft increases, making it difficult to reduce the size of the transmission.
Also, when a multi-speed transmission equipped with a plurality of clutches is mounted on a motorcycle, due to the structure of the motorcycle on which the transmission is mounted, it is necessary to position the center of gravity approximately centrally in the vehicle width direction together with the mounted engine, and therefore it is desirable to create a weight balance that is not biased toward the left or right.